Forming laminated sheet glass

Abstract

A first molten glass of one composition is caused to flow downwardly along converging flow paths of a forming member while simultaneously at least one other molten glass of a different composition is flown downwardly along outer surface portions of the first glass such that said glasses are in molten contact with one another during their downward travel and are then continuously formed into a composite or laminated glass sheet. The molten glasses are distributed to the forming member in such a manner as to provide substantially uniform thickness of the glass layers across the newly formed sheet, and various viscosity, glass flow rates and proportionate layer thicknesses may be obtained by varying the degree of tilt of the forming member.

We claim: 
     
       1. A method of forming laminated sheet glass which comprises, supplying a first molten glass of one composition to a first overflow channel, supplying a second molten glass of another composition to a second overflow channel, overflowing the first glass from said first channel into two separate downwardly converging sheet-like flow paths, overflowing the second glass from the second channel downwardly into two separate sheet-like flow paths and onto the outer surface of the downwardly flowing sheet-like paths of said first glass to form a pair of downwardly converging laminated flows while said glasses are in a molten condition, uniting said converging pairs of laminated flows into a single composite and drawing a sheet of laminated glass therefrom, and maintaining the outer surface of said second glass free from contact with distributing or forming means so as to provide a laminated glass sheet of fire polished quality. 
     
     
       2. A method of forming laminated sheet glass as defined in claim 1 including the steps of supplying at least one additional molten glass to a further overflow channel, overflowing the additional glass from said further channel into two separate sheet-like flow paths and onto the outer surface of the downwardly flowing sheet-like paths of said second glass to provide additional laminate flows while said glasses are in a molten condition. 
     
     
       3. A method of forming laminated sheet glass as defined in claim 1 including the steps of supplying a relatively fluid glass to said first overflow channel, supplying a devitrifiable glass to said second overflow channel at a viscosity greater than that of the relatively fluid glass supplied to said first overflow channel, and downwardly flowing said more viscous glass from said second overflow channel with a substantially slug flow pattern downwardly along the outer surface of the more fluid glass flow paths from said first overflow channel. 
     
     
       4. A method of forming laminated sheet glass as defined in claim 3 wherein the more fluid glass has a substantially laminar flow velocity with a maximum velocity adjacent to said more viscous glass and decreasing in velocity with increased distance from said more viscous glass. 
     
     
       5. A method of forming laminated sheet glass as defined in claim 1 including the steps of supplying the first molten glass to one end of said first overflow channel, and supplying the second molten glass to an end of said second flow channel which is opposite to the supply end of said first overflow channel. 
     
     
       6. A method of forming laminated sheet glass as defined in claim 1 or 5 which includes the steps of initially positioning longitudinal upper edge portions of each of said overflow channels at an angle relative to the horizontal, longitudinally tilting each said overflow channels to change the angle that the upper surfaces of each make with the horizontal so as to permit changes in glass flow rate and viscosity while maintaining substantially uniform flow from each channel. 
     
     
       7. A method of forming laminated sheet glass as defined in claim 6 including the step of tilting one of said overflow troughs so as to increase the angle which said longitudinal upper surfaces make with the horizontal and simultaneously tilting the other of said overflow channels so as to decrease the angle at which its longitudinal surfaces make with the horizontal thereby provides flexibility in the flow rates and viscosities of the glasses overflowing said channels while maintaining substantially uniform flow across the widths of the flow paths so formed. 
     
     
       8. A method of forming laminated sheet glass as defined in claim 1 including the step of feeding the drawn sheet of laminated glass to the surface of a molten metal bath and continuously moving such sheet across the surface of said bath. 
     
     
       9. Apparatus for forming laminated sheet glass which comprises, first overflow means for forming opposed sheetlike flows of molten glass having substantially uniform thickness across the width thereof, forming means positioned below said first overflow means for converging and uniting said opposed sheet-like flows into a single drawn sheet flow, second overflow means positioned above said first overflow means for overflowing second sheet-like flows of molten glass of substantially uniform thickness downwardly upon outer surfaces of said opposed sheet-like flows of said first overflow means, means for separately feeding molten glass to said first overflow means and said second overflow means, said first and second overflow means having longitudinally extending upper overflow surface portions, and means for longitudinally tilting said upper surface portions of said first and second overflow means with respect to the horizontal. 
     
     
       10. Apparatus for forming laminated sheet glass as defined in claim 9 wherein said first and second overflow means each comprises a longitudinally extending overflow channel having longitudinally extending upper overflow weir surfaces along each side of said channel and a glass delivery pipe communicating with an inlet end of each channel, and said upper overflow weir surfaces being substantially linear and extending from the inlet end at an angle below the horizontal. 
     
     
       11. Apparatus for forming laminated sheet glass as defined in claim 10 wherein the inlet end of one of said overflow channels is at an end of the channel opposite from the inlet end of the other of said channels, and the upper weir overflow surfaces of one of said overflow channels tapers downwardly below the horizontal from one side of said apparatus toward the other while the upper weir overflow surfaces of the other overflow channel taper downwardly below the horizontal from the other side of the apparatus toward said one side such that said means for tilting said upper surface portions increases the angle of tilt with respect to one of said channels and decreases said angle with respect to the other. 
     
     
       12. Apparatus for forming laminated sheet glass as defined in claim 9 which includes molten metal bath means for receiving upon the surface thereof the sheet flow drawn from said forming means.